| dc.description.abstract | Tauw bv proposes tidal creek restoration to bring back the tide into the upland area of
Zeeland in a safe and controllable manner. This will positively contribute to the Water
Framework Directive, ecological values and attractiveness of the region. However tidal
creek restoration may also lead to negative effects on the surrounding land use, current
knowledge is merely focused on the success rate of the ecological restoration. Within
this research a framework has been developed to evaluate locations for tidal creek
restoration, based on the effects on the surrounding land use. This framework will be
used to evaluate three locations, Zierikzee, Colijnsplaat and Sint Maartensdijk, which are
selected by Tauw bv.
The framework is mainly formed by a literature study and expert meetings, and handles
the relevant factors concerning evaluating locations for tidal creek restoration: safety
preconditions and wishes of stakeholders, show the possibilities and restrictions for tidal
creek restoration. The lateral extent of groundwater fluctuations and salinity intrusion
combined with their valued effects and the surface area of the affected types of land use
are the criteria which show the impact of tidal creek restoration on the surrounding land
use.
The preconditions in the Netherlands are set by “Wet op de Waterkering” of 1996 and
“Waterwet” of 2009 (www.wetten.overheid.nl). In order to ensure these safety standards,
the incoming tide via the tidal creek needs to be controlled and damped by water
constructions. Tidal creek restoration with the help of a water construction diminishes the
wave energy, so the tidal energy is the most important factor from the tidal regime. The
wishes of the stakeholders are set by expert meetings
To predict the lateral extent of groundwater fluctuations and salinity intrusion, landscape
analysis is needed to find the relevant parameters. The lateral extent of groundwater
fluctuations depends on whether the adjacent aquifer is a confined or unconfined
aquifer. Unconfined aquifers (Colijnsplaat; ± 200 m) showed a far less extent of
groundwater fluctuations compared to the confined aquifers (Zierikzee, Sint
Maartensdijk; ± 1,000 m). All the locations showed that the amplitude of the groundwater
fluctuations decreases exponentially with the distance. The lateral extent of the intrusion
of salinity is not depended on locations characteristic, only on the tidal period (which is
the same for all the three locations), and has a fixed distance of 60 meters.
The value of the effect is depending on the land use type, which for Zeeland ca be
divided in the following groups: urban areas, agriculture and nature areas. Groundwater
fluctuations have especially a negative influence to wooden foundations of constructions
in urban areas, due to bacterial decay. The most prominent negative effects of an
increase in salinity are on agriculture and most terrestrial nature areas as forests. Finally
a quantification of the surface area of a certain land use type with the given valued effect
is needed as it makes it able to compare different locations to each other.
Applying the framework to the three locations shows that the framework makes it easily
visible to see which, how and how much of a land use type is affected, which can help
policymakers to make their decision on which location is the “best option” for tidal creek
restoration. However this framework is not meant to point out the best location, it is a
tool in the evaluating process for policymakers. | |
